Polyethylene compositions comprising at least two or more distinct molecular weight ethylene copolymers are known in the art. Such compositions are often used in articles such as films and pipes. Typically, the composition that is useful for films is not useful for pipes or blow molded or rotomolded products. What would be useful is a “multimodal” polyethylene that is useful for all of these applications.
It is known that the type and amount of side chain branching within the multimodal polyethylenes can influence the final properties of an article made therefrom. In particular, K. Ebner, Bi-Modal HDPE for Piping Systems and Further Applications in ADV. PLAST. TECHNOL. APT, INT. CONF. 1-8 (1997) and J. Scheirs et al., PE100 Resins for Pipe Applications in 4(12) TRENDS IN POLY. SCI. 408-415 (1996) finds that bimodal polyethylenes having the majority of the branching on the relatively “high” molecular weight fraction are most ideal. Typically, polyethylenes useful in pipes, such as disclosed in U.S. Pat. No. 6,867,278, comprise a low and a high molecular weight composition, wherein most or all of the branching is located on the high molecular weight fraction. What has not been disclosed are polyethylenes having a desirable amount of branching that would allow the composition to be multifunctional. The inventors have found such a composition, and in particular, have surprisingly found that certain multimodal compositions having a relatively large amount of branching on the low molecular weight ethylene copolymer are high versatile and useful in both film and pipe applications, as well as in blow molding and injection molding applications.